Mechanism of pH Dependent Decomposition of Monoalkylamine Diazeniumdiolates to Form HNO and NO Deduced from the Model Compound Methylamine Diazeniumdiolate Density Functional Theory and CBS-QB3 Calculations

摘要

Isopropylamine diazeniumdiolate, IPA/NO, the product of the reaction of isopropylamine and nitric oxide, NO, decomposes in a pH dependent manner to afford nitroxyl, HNO, in the pH range of 13 to above 5 and NO below pH 7. Theoretical studies using B3LYP/6-311+G(d) density functional theory, the PCM and CPCM solvation models and the high accuracy CBS-QB3 method on the simplified model compound, methylamine diazeniumdiolate, predict a mechanism involving HNO production via decomposition of the unstable tautomer MeNN⁺(O⁻)NHO⁻. The production of NO at lower pH is predicted to result from fragmentation of the amide/NO adduct upon protonation of the amine nitrogen.